Hello folks. I’m hoping to get some guidance on trouble shooting my cadets. I have moderate experience in euro DIY but this is my first foray into visual which makes the trouble shooting a bit trickier for me, and I wasn’t good at it to begin with.
I built a Cadet 21 type setup. By the time I had the case ready to go, I already had all the modules built up, which I realize isn’t great from a trouble-shooting perspective. I was expecting trouble, but what I am getting is absolutely no output at all. By no output I mean on the screen - I’m registering about 1.7V on output 1 and 0.7 on output 2. TVs do not recognize an incoming signal.
I’ve stripped it down to everything but the sync generator, the RGB encoder, and oscillators. The oscillators appear to be working, and I have patched them into the RGB inputs, but I can get neither of two TVs tested to recognize any signal coming through the RCA from the encoder.
Sadly I do not have an oscilloscope. I checked the 7805 and the voltage seemed normal. I’m hoping someone here can give me some guidance on what other voltages I can check and perhaps what readings I should expect, or where I might focus my attention.
I’ve gone over the soldering, but it is difficult to trace the circuit from the schematic without knowing the layout of the components on the board. I’ve checked the polarity of all the components.
Any tips or suggestions are much appreciated! Cheers.
How are you testing the oscillators? Patching them to your other Euro stuff? I would guess that the VCOs still work when not receiving sync, but you may be able to check that sync is working without a scope by experimenting with the oscillators. For example by putting the VCOs in vertical range and flipping the sync switch, it should switch between a plain triangle wave and one that’s hard-synced to the field rate (60 Hz for NTSC / 50 Hz for PAL). This should sound different enough to allow figuring out if your sync generator is working correctly.
In my experience if the RGB encoder is not receiving sync, displays won’t register it at all - on my display I would get a solid blue “no input” screen, same as if I just disconnected the AV input. If you get a blue screen or “no input” indication when nothing is connected, but get a black screen when connecting to your RGB encoder, your encoder may be outputting sync but not encoding signals correctly (due to a bad solder joint / whatever).
If you are getting sync generated, I would guess you can also listen to the front panel vertical sync output to get a very low tone (50-60 Hz pulse wave) and a tone from the hsync output that may be too high-frequency to hear (>15 kHz). If you’re not getting sync output from Cadet I at all, but you don’t think there are any soldering issues or incorrect components, it might be worth trying to reprogram the microcontroller (though this will require an AVR programmer). Some discussion of the settings for doing this is here.
Hey, thanks for the input. It seems you’re right about the sync being the issue. I “tested” the oscs just by listening to them. Horizontal is very high but audible for much of the range, vertical is not what I would call “very low”, but much lower than horizontal. However flipping the sync switch has no effect on any of the oscillators. Which I guess means I need to switch my attention to the sync generator! I’ll see what I can discover with my multimeter there this afternoon.
Yes this sounds right, what I meant is that a working sync generator’s front panel outputs will also be audible if you patch directly from the “HΠ_” (very high pitched), “VΠ_” (square wave sound), or “FRAMEΠ_” (lower pitched square wave) outputs.
On listening to them you’re right that none of these sound “very low” as you get a lot of upper harmonics from the pulse waves. With the VCOs in vertical range but with sync off, I can hear a clean triangle wave that sweeps smoothly as I sweep the frequency knob. With sync engaged there is a buzzier tone and a pleasing sweep in harmonic content as I sweep the knob.
Best of luck with troubleshooting your sync gen! Aside from checking the power pins on the ICs, you may be able to check some functionality by setting your multimeter to frequency measurement mode.
If you’re confident your soldering on the sync generator is good, I would definitely check that the Atmega chip is programmed. I had a similar issue with either extremely erratic or no output in my system until I narrowed it down to that. The thread csboling referenced has good info, particularly on setting the fuses correctly.
Well I wouldn’t say I’m confident but I’ve traced the circuit now and as best as I can tell the soldering is good. I did actually find a couple jack lugs that I had missed but fixing that hasn’t changed the problem. It does though make me think it’s more likely something I fucked up than that the atmega isn’t programmed.
I don’t have a programmer and have zero experience programming microcontrollers. Is there a way to verify whether the atmega is programmed? I feel like I’m about as likely to break the thing as I am to fix it and would rather not get into that territory unless I’m quite sure that’s the issue.
EDIT: just read this thread which suggests it may be difficult to verify the atmega without a scope… Perhaps I will need to order up a programmer.
I read the power pins on the ICs and everything seems normal, as far as I can tell:
I was building 2 Sync generators. both Atmega’s were blank. I got send new ones, unfortunately those were blank too. (I have 1 older sync generator that works, so I can check the pcb’s)
So the possibility of this happening to you is high.
I don’t have my board in front of me to compare but nothing is jumping out at me as an obvious issue. My issue was similar in that my soldering was fine but the Atmega chip was blank. If you can find someone local to you who has access to an AVR ISP MKII programmer and a PC running Atmel Studio 7, that’s probably your best bet.
If you want to try it on your own, I used this programmer and once I got the settings correct in Atmel Studio based on the thread csboling linked before, it was really quick to upload to the Atmega chip: https://www.amazon.com/gp/product/B00KM6ZA9I
Okay cool, thanks for the input everyone, I really appreciate it. I live in the boons so I’ll have to order a programmer and figure how to flash the chip. I run Linux which I’m sure will add another delightful layer of complexity.
Hi @Whelm,
+1 for the unprogrammed ATMEGA. LZX sent me two blank ones too, on orders six months apart.
Programming is non-trivial if you haven’t done it before - I hadn’t and it took me a while to work out how to get everything right. And I’ve been a computer programmer since 1986!
But… it is very easy once you get all your ducks in a row.
If you are in the Australian or New Zealand “boonies” and would like me to program one for you, test that it works and then send it to you then please let me know and I’ll be happy to do so - I have a spare ATMEGA chip I bought while getting mine going.
Here’s the thread outlining my experience: Cadet Sync Generator Problem
Stay in touch because I’m here to make sure you don’t have the frustrating experience I did!
P.S. Your soldering looks pretty good, other than one pin on the IC in the top right corner (near the voltage regulator, third pin from the right on the bottom row of pins) which might be worth a quick check.
Hey, thanks for the offer, but I’m all the way in Canada. I’m waiting on a ATMEGA programmer to arrive in the mail over the next couple of weeks. Hopefully I can figure it out based on your thread and a couple others that have been posted. I’m no programmer but I do have some experience flashing packages onto phones and shit so… fingers crossed.
That’s a drag you had such a frustrating experience. =/ You’ll definitely be hearing from me if/when I get lost.
It’s disappointing that this issue seems so prevalent, given the number of people who have had multiple chips sent unprogrammed. I really appreicate LZX providing these boards and schematics to the DIY community with little financial incentive for themselves but still, this seems to have affected more than a couple chips.
Hi,
I can tell you my case. It was due to the RGB encoder AD724JRZ’s defect. That is pre-soldered on the pcb.
I spent one year to isolate the problem, indeed, and replaced the chip with new one. Then everything started to work well. Anything could happen. Pre - soldered chip might not be exception.
I do think you’d better buy a oscilloscope to understand what’s wrong. I used a 30$ DSO138.
Good luck.
So I’ve finally been able to get around to this, and the problem I’m now getting is that both avrdude and AVR Studio read a device signature of 0x0000c0, which is evidently incorrect, and programing fails.
I thought this might be an issue with avrdude and that waveshare programmer I bought, but the issue is the same with AVR Studio 6.
I looked this issue up on search engines and it returns discussions that are technical beyond me.
avrdude -c avrispmkII -p m88 -P usb -B 1 -U flash:w:LZX-C1-SW-V1.0.elf -U efuse:w:0xF9:m -U hfuse:w:0xDF:m -U lfuse:w:0xFF:m
avrdude: AVR device initialized and ready to accept instructions
Reading | ################################################## | 100% 0.00s
avrdude: Device signature = 0x000000 (retrying)
Reading | ################################################## | 100% 0.00s
avrdude: Device signature = 0x000000 (retrying)
Reading | ################################################## | 100% 0.00s
avrdude: Device signature = 0x000000
avrdude: Yikes! Invalid device signature.
Double check connections and try again, or use -F to override
this check.
I’m concerned that I’ve somehow bricked the chip. Suppose I’ll go over the soldering again…
I found this page that suggests changing avrdude’s clock speed as a solution but I don’t understand that biz.
changing the clock speed in Atmel Studio is quite easy at least.
A signature of 000000 pretty much just means you either are getting nothing back or that the MISO line is stuck low.
It’s entirely consistent with either a wrong/loose connection or short on the programming line, some form of brick or equivalently to a brick: Your mega having the correct fuse settings (i.e. external clock) but the clock missing.
Personally i’d try to eliminate the latter first. Do you have access to anything that could indicate whether the clock reaches pin PB6? Ideally a scope or frequency meter, but just a voltmeter reading indicating some DC component midway between 0 and 5V would help
I am too trying to get AVRDude to put the firmware on my chips.
I’m getting a ‘out of sync’ message. Does anyone know what that means exactly and how to fix it?
Googling suggests it’s related to the communication between the computer and the programmer, so the first thing to check is that the flags you’re using are right for your programmer - USB or another interface type? - and that the programmer type is correct. Check https://www.nongnu.org/avrdude/user-manual/avrdude_4.html for more information, particularly the “-c” option to specify the programmer.
